The invention relates to a basket forceps assembly for use with an endoscope, and more particularly, to an assembly which may be used in a medical endoscope to recover and remove any foreign matter located within a coelom such as a gallstone or ureteral calculus.
Recently, endoscopes have found extensive applications. Present endoscopes have an insertable portion of a reduced cross section and an increased length. The distal end of the insertable portion is adapted to emit light for illumination, thus enabling the observation of the interior of an illuminated coelom.
The insertable portion of the endoscope is capable of receiving a treatment instrument such as a baket forceps assembly for passage therethrough. The treatment instrument may be inserted through the insertable portion so as to enable the instrument to pick the tissue of an affected area located within the coelom for a detailed diagnosis of such part or to remove unwanted matters, such as calculi, which happen to form within the bile duct or ureter.
Where the calculus has grown to an increased size, a basket forceps assembly such as the device disclosed in Japanese Laid-Open Utility Model Application No. 109,705/1981, may be used. Specifically, a basket is formed on the distal end of the forceps assembly and is designed to receive a calculus therein, whereupon it may be closed to fracture and eliminate the calculus, by pulling a slider at the proximal end of the forceps assembly rearwardly.
A variety of such basket forceps assemblies are known, including an assembly of the type in which a water supply inlet is formed in the proximal end of the forceps assembly and is connected to the hollow interior of a flexible sheath through which an operating wire may be passed, thus allowing water or a fluid, such as a contrast agent, to be delivered through the front end of the flexible sheath. With this basket forceps assembly having a water outlet, there is no difficulty in maintaining a water supply when the individual resilient wires, which together form the basket, project beyond the front end of the sheath. However, when these wires are retracted to their stowed position within the flexible sheath and a front end tip to which the individual wires are fixedly connected is fitted into the front end of the sheath, the delivery of water or fluid is inhibited or rendered difficult, inasmuch as the opening in the front end of the sheath is effectively plugged by the front end tip. If an increased supply pressure is used, the water may be delivered in small quantities through a gap formed between the fitting parts. However, this method of delivering water is unreliable and adds to the burden of an operator who is operating the endoscope Additionally, it takes an increased length of time to complete the supply of a given amount of water. Additional disadvantages which are involved with supplying water under increased pressure include the likelihood that the front end tip may be disengaged from the free ends of the wires to be left within the coelom or that the force which caused the disengagement may also cause the tip or the expanding resilient wires to impact upon the internal wall of the coelom, which may then be injured. Even if the disengagement of the tip is prevented, the tip may still be driven forward under the increased water pressure, allowing a burst of water to be delivered at one time, making it difficult to maintain a reliable control over the amount of water supplied.
Water supply is permitted if the front end tip is maintained at a position projecting out of the front end of the sheath rather than blocking the latter. However, when the basket is not stowed within the sheath and the front end tip is not reliably secured in position as by fitting it in the front end of the sheath, such as when no calculus fracturing operation takes place or when a calculus is not held by the basket, the individual wires which form the basket are biased or urged to expand as they project, so that they may impact upon the internal wall of the coelom. Accordingly, maintaining the front end tip at its projecting position is undesirable for safety reasons.
In addition, if an operator is required to supply water when the free end tip is projecting, extreme care is required of the operator to note the degree to which the basket has been expanded or to watch if it is maintained in a condition to avoid any injury to the internal wall of the coelom. Thus, an increased burden on the part of the operator is necessarily required, which represents a major disadvantage.